If you want to be an egocentric arse there is an even faster way than just cycling through sector space. (At least for the more popular nebulas).
Assuming that you know the general anomaly layout line yourself up in front of a good route (three fast grabs), log out once to save your position in the nebula. And then go hunting.
Grab the data on your route, switch instance, enter 'new' instance on the position you saved because of logging out, grab the data there on your route, enter next instance, etc. pp.
Do not under any circumstances enter an explore system node when using that method.